多继承构造函数和析构函数的执行顺序与单继承相同,但应强调的是,基类之间的执行顺序是严格按照声明时从左到右的顺序来执行的,与他们在定义派生类构造函数中的次序无关。例如:
#include<iostream>
using namespace std;
class Base1{
int x1;
public:
Base1(int y1)
{
x1=y1;
cout<<"Constructing Base1, x1= "<<x1<<endl;
}
~Base1()
{
cout<<"Destructing Base1"<<endl;
}
};
class Base2
{
int x2;
public:
Base2(int y2)
{
x2=y2;
cout<<"Constructing Base2, x2= "<<x2<<endl;
}
~Base2()
{
cout<<"Destructing Base2"<<endl;
}
};
class Base3
{
public:
Base3()
{
cout<<"Constructing Base3"<<endl;
}
~Base3()
{
cout<<"Destructing Base3"<<endl;
}
};
class Derived: public Base2,public Base1,public Base3//基类之间的执行顺序是严格按照声明时从左到右的顺序来执行的,与他们在定义派生类构造函数中的次序无关。
{
private:
Base1 ob1;
Base2 ob2;
Base3 ob3;
public:
Derived(int x,int y,int z,int v):Base1(x),Base2(y),ob1(z),ob2(v)//对于使用默认构造函数的基类或对象成员(Base3,ob3),可以不写在参数表达式表里
{
cout<<"Constructing Derived"<<endl;
}
};
int main()
{
Derived ob(1,2,3,4);//Derived(1,2,3,4);
system("pause");
}

上例中,创建派生类的对象ob时,依次调用基类Base2,Base1,Base3,最后调用派生类Derived的构造函数。有释放对象调用析构函数时,其顺序正好与构造函数的顺序相反。